The present invention relates to a method of manufacturing an enclosure for an automotive passenger restraint airbag. More particularly, the present invention relates to a method of forming an electric heating element in or on the enclosure.
U.S. Pat. No. 6,070,901 teaches a method of manufacturing an automotive instrument panel (IP) wherein a laser is used to score the IP in order to form an invisible seam around an airbag deployment opening in the IP. The laser is directed from a position adjacent the inner surface of the multi-layer IP and cuts through all but the outermost layer of the IP to form a fracturable airbag deployment path that offers minimal resistance to deployment of the airbag.
A consideration in the design of IPs and other types of airbag enclosures is the fact that many plastic materials from which these structures are typically formed tend to become brittle at low temperatures. For proper functioning of the airbag, it is necessary that the portion of the enclosure covering the airbag and through which it deploys be formed of a material that will remain suitably soft and ductile throughout a broad range of ambient operating temperatures. This consideration results in the ruling out of many plastics that, because of other desirable characteristics, might otherwise be appropriate for use.
U.S. Pat. No. 5,372,379 teaches an automotive IP having a thermostatically controlled electric heater disposed adjacent a deployment plate or opening, the heater maintaining the structure adjacent the airbag at a desired minimum temperature. The heater eliminates the need to select an IP covering material that does not become unduly brittle at low temperatures, thus reducing the number of compromises that must be made during the design of the IP.
The present invention is directed to an improved and simplified method of manufacturing an automotive airbag enclosure, such as an instrument panel (IP), having an opening for deployment therethrough of an airbag and an electric heating element disposed adjacent the opening for protecting against brittle fracture of the enclosure during deployment of the airbag. The method is adapted for use with a process for forming a seamless airbag cover wherein a laser is used to score a multi-layer IP construction from the inside, cutting completely through all but the outermost layer covering the airbag prior to deployment.
According to a first aspect of the invention, the method comprises the steps of forming a layer of an airbag enclosure having outer and inner surfaces, providing an electrically conductive strip adjacent the inner surface of the layer to define at least a portion of a perimeter of the airbag opening, and directing a high intensity light beam toward the strip to completely penetrate the strip. The laser divides the strip into two parallel conductive paths, whereby the strip may be supplied with electric current and serve as the electrical heating element.
The invention may be easily manufactured because the covering, conductive strip, plate, foam and substrate are all assembled prior to forming an aperture in the substrate.
These and other advantages of the present invention will become more apparent in the course of the following detailed description and appended claims. The invention may best be understood with reference to the accompanying drawings wherein illustrative embodiments are shown.